This invention relates to a switch which is required to meet specifications having high contact reliability, such as a switch which is built in a controller button of a game machine.
In convention, as a switch of a type whose contacts are brought into a conductive state by pressing a plunger, for example, various switches have been developed for obtaining sufficient contact pressure at the contacts, and excellent feeling of press operation of the plunger.
For example, one of them is disclosed in Japanese Utility Model Publication No. 4-22500 as a “miniature switch”.
The “miniature switch” of Japanese Utility Model Publication No. 4-22500 is constituted by a housing which is configured by a switch base, and a switch cover fitted into the switch base, a plunger which slides upward and downward with respect to the housing, and a spring which is mounted between the housing and the plunger.
Further, as a spring, the above-mentioned “miniature switch” uses a special spring which is configured by a small diameter coil portion, and a conical large diameter coil portion which is formed with a lager diameter than that of the small diameter coil portion, the small diameter coil portion and the large diameter coil portion being disposed in series. In the constitution, the large diameter coil portion is a movable contact, and a fixed contact portion is formed at a point of the housing which is opposite to the large diameter coil portion so as to move closer to and apart from the same.
Japanese Utility Model Publication No. 4-22500 describes the following advantageous effect that, as mentioned above, by providing the large diameter coil portion to the spring, when being compressed, overlapping of the wires each other can be prevented so that a long stroke in the compression direction can be ensured.
However, in the case of the constitution, like the “miniature switch” of Japanese Utility Model Publication No. 4-22500, in which the large diameter coil portion and the small diameter coil portion are disposed in series, when the plunger is pressed, a desired elastic property cannot be obtained with respect to the spring for bias in the return direction.
For details, generally, when an operator presses the plunger of the switch, just after pressing, the operator receives elastic force from the spring as press load from the plunger so that the operator can recognize his/her pressing of the plunger as perception, thereby obtaining feeling of press operation.
However, in the case of the spring which is provided to the “miniature switch” of Japanese Utility Model Publication No. 4-22500, the large diameter coil portion is more easily deformed elastically, in comparison to the small diameter coil portion. Therefore, when being pressed by a slide of the plunger, first, the large diameter coil portion having a lower elastic modulus, in comparison to the small diameter coil portion, is elastically deformed unduly so that the build-up of elastic force by the press becomes slow.
As a result, even when the operator presses the plunger, the operator does not receive a moderate load from the plunger by the press, and the plunger is pressed down. Therefore, there are some problems that it is difficult for the operator, like perceiving the press, and the feeling of press operation is deteriorated.
On the other hand, Japanese Utility Model Laid-Open Publication No. 6-15232 proposes a “push button switch”.
The “push button switch” of Japanese Utility Model Laid-Open Publication No. 6-15232 includes a push button which can be pushed downward, a pair of terminals which are brought into a conductive state by contact of a contact spring, and two kinds of springs, i.e., a return spring and a contact spring.
The contact spring is disposed outside (on the upper side of) the push button, and is held under a compressed state by a spring holding portion which is disposed at a lower portion of the push button. The spring holding portion is biased in the press down direction with weak force by the return spring, and from the time point when the spring holding portion is pressed down lower than the pair of terminals, the return spring makes contact with the pair of terminals so as to bring the pair of terminals into a conductive state therebetween.
The above-mentioned “push button switch” of Japanese Utility Model Laid-Open Publication No. 6-15232 is provided with two kinds of springs, i.e., the return spring and the contact spring which are separately disposed, so that the return spring having a moderate elastic property is elastically deformed just after the operator presses the push button. Therefore, it is expected to produce an advantageous effect that the operator can perceive moderate feeling by the press from the push button just after pressing.
However, in the “push button switch” of Japanese Utility Model Laid-Open Publication No. 6-15232, as the push button is pressed, the spring holding portion is pressed downward, and the contact spring becomes to make contact with the pair of terminals from the time point when the spring holding portion is located lower than the pair of terminals. But, even when the push button is further pressed, the contact pressure against the pair of terminals is constant because the length of the contact spring does not change.
Namely, in the “push button switch” of Japanese Utility Model Laid-Open Publication No. 6-15232, once the contact spring has made contact with the pair of terminals, even when the push button is pressed, the contact pressure between the contact spring and the pair of terminals has already reached the limit. Moreover, the contact spring is disposed in a mode in which the contact spring is expanded as the push button for the holding portion is pressed until making contact with the pair of terminals. Therefore, there is a restriction that the force by the elasticity for biasing the spring holding portion in the press down direction is weaker than the force by the return spring. Accordingly, it should be difficult for the constitution to ensure sufficient contact pressure against the pair of terminals.
Accordingly, the “push button switch” of Japanese Utility Model Laid-Open Publication No. 6-15232 has a problem that reliability of the electrical conduction cannot be ensured.
Moreover, in the “push button switch” of Japanese Utility Model Laid-Open Publication No. 6-15232, the feeling of pressing hardly change after the contact spring makes contact with the pair of terminals, and therefore, it is practically impossible to perceive the fact that the contact spring has made contact with the pair of terminals. Accordingly, there is another problem that an operator cannot obtain satisfactory feeling of operation.